Traditionally, processing compositions for silver halide photographic light-sensitive materials are used in the form of liquid or powder. When the processing composition is liquid, it is used as such or after being mixed with water in an optionally selected ratio. When it is powder, it is used after being dissolved in water.
However, in the case of liquid compositions, the presence of water therein increases both volume and weight, thus posing problems related to transportation cost and liquid leakage and other safety concerns, though they are easy to dissolve. In addition, when a large amount is handled, great weight is a significant burden on the user. In the case of powder agents, powder scattering poses a problem related to the working environment, though they much surpass liquid compositions in compactness.
Also, both liquid and powder compositions pose a problem of environmental pollution upon disposal due to the residence of the liquid or powder in the packing material after solution preparation.
To solve these problems, a number of methods wherein the processing composition is granulated or tableted are under investigation in the photographic industry.
In the production of granules or tablets, it is a common practice to uniformly mix a small amount of water and binders such as starch, polyvinyl alcohol, cellulose and gelatin, which binders are used to ensure a sufficient level of strength of the granules or tablets obtained, with the base components and either granulate the mixture by extrusion granulation, mixing stirring granulation or another granulating method or tablet the mixture by compressive forming. Then, the residual water is removed through the drying process to yield a finished product.
However, granulation using water is undesirable for photographic processing components, especially developing components, because their storage stability is significantly affected by the residual water therein. Although the residual water content can be reduced by drying, drying deteriorates the strength of granules or tablets, which can lead to dust formation due to vibrating destruction during transportation and poses a problem similar to that occurring in powder processing compositions, and more importantly, it raises production cost considerably.
A photographic processing composition usually contains organic compounds such as a developing agent, a developing inhibitor, a developing accelerator, an anti-silver sludge agent and a gamma value regulator. With the recent technical improvements, the number of organic compounds used and the number of their kinds have tended to increase.
In the case of liquid processing compositions, organic solvents can be used, in which the above-mentioned organic compounds can be dissolved, which offers a great advantage over powder processing compositions. However, although organic solvents can be present at several percentages of the total amount of base components, this amount is insufficient to dissolve the above-mentioned organic compounds; increasing the organic solvent content deteriorates the mechanical strength and storage stability of granules or tablets. Moreover, the use of a large amount of organic solvent is also undesirable from the point of view of environmental protection.